The invention concerns an electroluminescence light arrangement of the kind known for example from laid-open German application DE-OS) No 198 02 269. That publication describes planar electrode arrangements which are provided on a circuit board substrate in relation to which an ac voltage is applied to two comb-shaped mutually interlaced electrodes (interdigital electrodes), in order to cause an electroluminescence layer applied by printing to those electrodes to light up. That layer can include a carrier substance which is a good electrical insulator so that there is no need for a separate insulation layer. If the two electrodes are disposed in the same plane, there must be a minimum spacing between them and an excessively high ac voltage may not be applied so that no electrical short-circuits occur. Under those conditions however, only a very weak electroluminescence lighting effect can be achieved with such an arrangement.
To resolve that problem, the above-indicated publication proposes that the two electrodes are to be arranged in different planes, that is to say one is to be arranged higher than the other, while a layer comprising a dielectric which is a good electrical insulator is to be provided between them. In the projection direction which is perpendicular to the surface covered by the electrodes and in which the electroluminescence lights are perceived, the horizontal spacings of the electrodes can then be as small as may be desired and may even be made zero as in fact the vertical spacing provides for sufficient electrical insulation. A disadvantage with that arrangement is that an increased number of layers have to be applied to the carrier substrate, whereby the manufacturing costs are increased, and in particular the at least two electrodes cannot be produced in a single working operation from the metallic coating which covers the carrier substrate.
In comparison therewith the object of the present invention is to develop an electroluminescence light arrangement of the kind set forth in the opening part of this specification, in such a way that the at least two electrodes can be provided in the same surface and nonetheless it is possible to achieve a marked increase in the brightness of the electroluminescence lighting effect.
It has surprisingly been found that, with the same amplitude and frequency of the ac voltage applied between the two electrodes, the light yield which can be attained is considerably improved by applying over the electroluminescence or pigment layer a thin cover layer which is transparent but a good electrical conductor and which does not have any contacts that lead outwardly. A particular advantage is that the difficulties which otherwise occur in terms of contacting thin transparent cover electrodes are completely eliminated here.
Advantageous configurations of the electroluminescence light arrangement according to the invention are set forth in the appendant claims.